1. Field of the Invention
This invention relates to a subject position adjustment apparatus for use with a laser interferometer.
2. Description of Related Art
Laser interferometers are typically accompanied by position adjustable stages on which a subject to be analyzed or measured is placed. For positionally adjusting a subject in any desired direction, some laser interferometers, of a type directing a laser beam downward toward the subject, have a position adjustable stage with a bi-directional position adjusting means, such as an X-Y stage, placed on a stationary base of the interferometer. Such laser interferometers also include a mono-directional position adjusting means, disposed on the bi-directional position adjusting means, on which the subject is actually placed.
Reference is made to FIG. 1, which shows a typical position adjustable stage, for the purpose of providing a brief background explanation that will enhance an understanding of the position adjustment of a laser interferometer stage.
A position adjustable stage 100 of a laser interferometer includes a bi-directional position adjusting or X-Y stage 101, placed on a stationary base 102 of the laser interferometer, and a mono-directional position adjusting or vertical position adjusting stand 103, disposed on the X-Y stage 101. The vertical position adjusting stand 103 is provided with a subject table 104 on which a subject to be measured is placed in an optical axis Xo of an objective lens Lo of the laser interferometer. Positioning of the subject is performed by operating the X-Y stage 101 so as to move the subject in two horizontal directions perpendicular to each other and by operating the vertical position adjusting stage 103 to move the subject up or down along the optical axis Xo. These operations may be performed in this order or vice versa.
If the direction in which the vertical position adjusting stage 103 moves to adjust a subject in vertical position is not parallel to the optical axis Xo of the laser interferometer, both the X-Y stage 101 and the vertical position adjusting stage 103 must be repeatedly operated in order to keep an interference pattern within a view field of an operator or a view field of a monitor camera.
In order to support the vertical position adjusting stage 103 on the X-Y stage 101, the X-Y stage 101 must be structurally rigid, unavoidably leading to large stage size. As a result, adjusting knobs of the X-Y stage 101, which are separated by a long distance, are somewhat troublesome to operate. In addition, since the stage 104, supported on the vertical position adjusting stage 103, has a vertical movement which is limited and small, measurement is restricted to small and, in particular, relatively thin subjects.